The are at least twelve different and incompatible styles of power plugs and sockets in use throughout the world today. These are represented in FIGS. 1A-1M. Table I summarizes which ones are in use in various countries, and the voltage and line frequencies used there. Voltages span 110V to 240V, and line frequencies are either 50 Hz or 60 Hz. Two and sometimes three pins or blades are used, and the size and position of the pins and blades vary with each type. The third electrode is usually a ground used in three-wire systems.
Modern electronic appliances are able to operate automatically with any of these voltages and frequencies, it's the plug arrangements that give trouble. But, larger appliances with motors must be operated with only one choice, 110V or 220V, and 50 Hz or 60 Hz. The United States is a rather large area that agrees all on the same style, FIGS. 1A-1B, so getting the correct plug is not usually a problem with 110V appliances. Dryers and other 220V appliances in the US do have a variety of incompatible plugs that are intended to match the current ratings, e.g., 30 A or 50 A. International travelers, and purchasers of international products are the ones who frequently must deal with power plug incompatibilities.
TABLE ICOUNTRYVOLTAGEFREQUENCYPLUGAfghanistan220 V50 HzFIG. 1C, FIG. 1FAlbania220 V50 HzFIG. 1C, FIG. 1FAlgeria230 V50 HzFIG. 1C, FIG. 1FAmerican Samoa120 V60 HzFIG. 1A, FIG. 1B, FIG. 1F, FIG. 1IAndorra230 V50 HzFIG. 1C, FIG. 1FAngola220 V50 HzFIG. 1CAnguilla110 V60 HzFIG. 1A (maybe FIG. 1B)Antigua230 V60 HzFIG. 1A, FIG. 1BArgentina220 V50 HzFIG. 1C, FIG. 1IArmenia220 V50 HzFIG. 1C, FIG. 1FAruba127 V60 HzFIG. 1A, FIG. 1B, FIG. 1FAustralia230 V50 HzFIG. 1IAustria230 V50 HzFIG. 1C, FIG. 1FAzerbaijan220 V50 HzFIG. 1C, FIG. 1FAzores220 V50 HzFIG. 1B, FIG. 1C, FIG. 1FBahamas120 V60 HzFIG. 1A, FIG. 1BBahrain230 V50 HzFIG. 1GAwali110 V60 HzFIG. 1GBalearic Islands220 V50 HzFIG. 1C, FIG. 1FBangladesh220 V50 HzFIG. 1A, FIG. 1C, FIG. 1D, FIG. 1G, FIG. 1KBarbados115 V50 HzFIG. 1A, FIG. 1BBelarus220 V50 HzFIG. 1C, FIG. 1FBelgium230 V50 HzFIG. 1EBelize110/220 V   60 HzFIG. 1B, FIG. 1GBenin220 V50 HzFIG. 1EBermuda120 V60 HzFIG. 1A, FIG. 1BBhutan230 V50 HzFIG. 1D, FIG. 1F, FIG. 1G FIG. 1MBolivia220/230 V   50 HzFIG. 1A, FIG. 1CBosnia220 V50 HzFIG. 1C, FIG. 1FBotswana231 V50 HzFIG. 1G, FIG. 1MBrazil110/220 V   60 HzFIG. 1A, FIG. 1B, FIG. 1CBrunei240 V50 HzFIG. 1GBulgaria230 V50 HzFIG. 1C, FIG. 1FBurkina Faso220 V50 HzFIG. 1C, FIG. 1EBurundi220 V50 HzFIG. 1C, FIG. 1ECambodia230 V50 HzFIG. 1A, FIG. 1CCanada120 V60 HzFIG. 1A, FIG. 1BCanary Islands220 V50 HzFIG. 1C, FIG. 1E, FIG. 1LCape Verde220 V50 HzFIG. 1C, FIG. 1FCayman Islands120 V60 HzFIG. 1A, FIG. 1BCentral African Rep220 V50 HzFIG. 1C, FIG. 1EChad220 V50 HzFIG. 1D, FIG. 1E, FIG. 1FChannel Islands230 V50 HzFIG. 1GChile220 V50 HzFIG. 1C, FIG. 1LChina, People's Rep220 V50 HzFIG. 1A, FIG. 1I, FIG. 1GColombia110 V60 HzFIG. 1A, FIG. 1BComoros220 V50 HzFIG. 1C, FIG. 1ECongo, People's Rep230 V50 HzFIG. 1C, FIG. 1ECongo, Dem. Rep220 V50 HzFIG. 1C, FIG. 1DCook Islands240 V50 HzFIG. 1ICosta Rica120 V60 HzFIG. 1A, FIG. 1BCôte d'Ivoire (Ivory Coast)220 V50 HzFIG. 1C, FIG. 1ECroatia230 V50 HzFIG. 1C, FIG. 1FCuba110/220 V   60 HzFIG. 1A, FIG. 1B, FIG. 1C, FIG. 1F, FIG. 1LCyprus240 V50 HzFIG. 1GCzech Republic230 V50 HzFIG. 1EDenmark230 V50 HzFIG. 1C, FIG. 1KDjibouti220 V50 HzFIG. 1C, FIG. 1EDominica230 V50 HzFIG. 1D, FIG. 1GDominican Republic110 V60 HzFIG. 1A Type FIG. 1JEast Timor220 V50 HzFIG. 1C, FIG. 1E, FIG. 1F, FIG. 1I,Ecuador120–127 V  60 HzFIG. 1A, FIG. 1BEgypt220 V50 HzFIG. 1CEl Salvador115 V60 HzFIG. 1A–1G, FIGS. 1I–1LEquatorial Guinea220 V50 HzFIG. 1C, FIG. 1EEritrea230 V50 HzFIG. 1CEstonia230 V50 HzFIG. 1FEthiopia220 V50 HzFIG. 1D, FIG. 1J, FIG. 1LFaeroe Islands220 V50 HzFIG. 1C, FIG. 1KFalkland Islands240 V50 HzFIG. 1GFiji240 V50 HzFIG. 1IFinland230 V50 HzFIG. 1C, FIG. 1FFrance230 V50 HzFIG. 1EFrench Guiana220 V50 HzFIG. 1C, FIG. 1EGaza230 V50 HzFIG. 1HGabon220 V50 HzFIG. 1CGambia230 V50 HzFIG. 1GGermany230 V50 HzFIG. 1C, FIG. 1FGhana230 V50 HzFIG. 1D, FIG. 1GGibraltar240 V50 HzFIG. 1C, FIG. 1GGreece220 V50 HzFIG. 1C, FIG. 1D, FIG. 1E, FIG. 1FGreenland220 V50 HzFIG. 1C, FIG. 1KGrenada230 V50 HzFIG. 1GGuadeloupe230 V50 HzFIG. 1C, FIG. 1D, FIG. 1EGuam110 V60 HzFIG. 1A, FIG. 1BGuatemala120 V60 HzFIG. 1A, FIG. 1B, FIG. 1G, FIG. 1IGuinea220 V50 HzFIG. 1C, FIG. 1F, FIG. 1KGuinea-Bissau220 V50 HzFIG. 1CGuyana240 V60 HzHaiti110 V60 HzFIG. 1A, FIG. 1BHonduras110 V60 HzFIG. 1A, FIG. 1BHong Kong220 V50 HzFIG. 1G, FIG. 1MHungary230 V50 HzFIG. 1C, FIG. 1FIceland220 V50 HzFIG. 1C, FIG. 1FIndia230 V50 HzFIG. 1C, FIG. 1DIndonesia127/230 V   50 HzFIG. 1C, FIG. 1F, FIG. 1GIran230 V50 HzFIG. 1CIraq230 V50 HzFIG. 1C, FIG. 1D, FIG. 1GIreland (Eire)23050 HzFIG. 1G Type FIG. 1FIsle of Man240 V50 HzFIG. 1C, FIG. 1GIsrael230 V50 HzFIG. 1H, FIG. 1CItaly230 V50 HzFIG. 1C, FIG. 1F, FIG. 1L Type FIG. 1LJamaica110 V50 HzFIG. 1A, FIG. 1BJapan100 V50/60 Hz  FIG. 1A, FIG. 1BEastern Japan 50 Hz(Tokyo, Kawasaki, Sapporo, Yokohoma, and Sendai)Western Japan 60 Hz(Osaka, Kyoto, Nagoya, Hiroshima)Jordan230 V50 HzFIG. 1D, FIG. 1F, FIG. 1G, FIG. 1J Type FIG. 1CKenya240 V50 HzFIG. 1GKazakhstan220 V50 HzFIG. 1CKiribati240 V50 HzFIG. 1IKorea, South220 V60 HzFIG. 1C, FIG. 1FKuwait240 V50 HzFIG. 1C, FIG. 1GLaos230 V50 HzFIG. 1A, FIG. 1B, FIG. 1C, FIG. 1E, FIG. 1FLatvia220 V50 HzFIG. 1C, FIG. 1FLebanon110/220 V   50 HzFIG. 1A, FIG. 1B, FIG. 1C, FIG. 1D, FIG. 1GLesotho220 V50 HzFIG. 1MLiberia120 V60 HzFIG. 1A, FIG. 1BLibya127 V50 HzFIG. 1DLithuania220 V50 HzFIG. 1C, FIG. 1FLiechtenstein230 V50 HzFIG. 1JLuxembourg220 V50 HzFIG. 1C, FIG. 1FMacau220 V50 HzFIG. 1D, FIG. 1GMacedonia220 V50 HzFIG. 1C, FIG. 1FMadagascar220 V50 HzFIG. 1C, FIG. 1EMadeira220 V50 HzFIG. 1C, FIG. 1FMalawi230 V50 HzFIG. 1GMalaysia240 V50 HzFIG. 1GMaldives230 V50 HzFIG. 1A, FIG. 1D, FIG. 1G, FIG. 1J, FIG. 1K, FIG. 1LMali220 V50 HzFIG. 1C, FIG. 1EMalta240 V50 HzFIG. 1GMartinique220 V50 HzFIG. 1C, FIG. 1D, FIG. 1EMauritania220 V50 HzFIG. 1CMauritius230 V50 HzFIG. 1C, FIG. 1GMexico127 V60 HzFIG. 1A, FIG. 1BMicronesia120 V60 HzFIG. 1A, FIG. 1BMonaco127/220 V   50 HzFIG. 1C, FIG. 1D, FIG. 1E FIG. 1FMongolia230 VFIG. 1C, FIG. 1EMontserrat230 V60 HzFIG. 1A, FIG. 1BMorocco127/220 V   50 HzFIG. 1C, FIG. 1EMozambique220 V50 HzFIG. 1C, FIG. 1F, FIG. 1MMyanmar230 V50 HzFIG. 1C, FIG. 1D, FIG. 1F, FIG. 1GNamibia220 V50 HzFIG. 1DNauru240 V50 HzFIG. 1INepal230 V50 HzFIG. 1C, FIG. 1DNetherlands230 V50 HzFIG. 1C, FIG. 1FNetherlands Antilles127/220 V   50 HzFIG. 1A, FIG. 1B, FIG. 1FSt. Martin120 V60 HzSaba, (St. Eustatius110 V60 HzFIG. 1A, maybe FIG. 1BNew Caledonia220 V50 HzFIG. 1FNew Zealand230 V50 HzFIG. 1INicaragua120 V60 HzFIG. 1ANiger220 V50 HzFIG. 1A, FIG. 1B, FIG. 1C, FIG. 1D, FIG. 1E, FIG. 1FNigeria240 V50 HzFIG. 1D, FIG. 1GNorway230 V50 HzFIG. 1C, FIG. 1FOkinawa100 V60 HzFIG. 1A, FIG. 1B, FIG. 1IOman240 V50 HzFIG. 1GPakistan230 V50 HzFIG. 1C, FIG. 1DPalmyra Atoll120 V60 HzFIG. 1A, FIG. 1BPanama110 V60 HzFIG. 1A, FIG. 1BPanama City120 VPapua New Guinea240 V50 HzFIG. 1IParaguay220 V50 HzFIG. 1CPeru220 V60 HzFIG. 1A, FIG. 1B, FIG. 1CPhilippines220 V60 HzFIG. 1A, FIG. 1B, FIG. 1CPoland230 V50 HzFIG. 1C, FIG. 1EPortugal230 V50 HzFIG. 1C, FIG. 1FPuerto Rico120 V60 HzFIG. 1A, FIG. 1BQatar240 V50 HzFIG. 1D, FIG. 1GRéunion Island220 V50 HzFIG. 1ERomania230 V50 HzFIG. 1C, FIG. 1FRussian Federation220 V50 HzFIG. 1CRwanda230 V50 HzFIG. 1C, FIG. 1JSt. Kitts and Nevis230 V60 HzFIG. 1D, FIG. 1GSt. Lucia240 V50 HzFIG. 1GSt. Vincent230 V50 HzFIG. 1A, FIG. 1C, FIG. 1E, FIG. 1G, FIG. 1I, FIG. 1KSaudi Arabia127/220 V   60 HzFIG. 1A, FIG. 1B, FIG. 1F, FIG. 1GSenegal230 V50 HzFIG. 1C, FIG. 1D, FIG. 1E, FIG. 1KSerbia-Montenegro220 V50 HzFIG. 1C, FIG. 1FSeychelles240 V50 HzFIG. 1GSierra Leone230 V50 HzFIG. 1D, FIG. 1GSingapore230 V50 HzFIG. 1G Type FIG. 1ASlovak Republic230 V50 HzFIG. 1ESlovenia220 V50 HzFIG. 1C, FIG. 1FSomalia220 V50 HzFIG. 1CSouth Africa220/230 V   50 HzFIG. 1MSpain230 V50 HzFIG. 1C, FIG. 1FSri Lanka230 V50 HzFIG. 1DSudan230 V50 HzFIG. 1C, FIG. 1DSuriname127 V60 HzFIG. 1C, FIG. 1FSwaziland230 V50 HzFIG. 1MSweden230 V50 HzFIG. 1C, FIG. 1FSwitzerland230 V50 HzFIG. 1J Type FIG. 1CSyria220 V50 HzFIG. 1C, FIG. 1E, FIG. 1LTahiti110/220 V   60 HzFIG. 1A, FIG. 1B, FIG. 1ETajikistan220 V50 HzFIG. 1C, FIG. 1ITaiwan110 V60 HzFIG. 1A, FIG. 1BTanzania230 V50 HzFIG. 1D, FIG. 1GThailand220 V50 HzFIG. 1A, FIG. 1CTogo220 V50 HzFIG. 1CTonga240 V50 HzFIG. 1ITrinidad, Tobago115 V60 HzFIG. 1A, FIG. 1BTunisia230 V50 HzFIG. 1C, FIG. 1ETurkey230 V50 HzFIG. 1C, FIG. 1FTurkmenistan220 V50 HzFIG. 1B, FIG. 1FUganda240 V50 HzFIG. 1GUkraine220 V50 HzFIG. 1CUnited Arab Emirates220 V50 HzFIG. 1C, FIG. 1D, FIG. 1GUnited Kingdom230 V50 HzFIG. 1GUnited States120 V60 HzFIG. 1A, FIG. 1BUruguay220 V50 HzFIG. 1C, FIG. 1F, FIG. 1I, FIG. 1L Type FIG. 1FUzbekistan220 V50 HzFIG. 1C, FIG. 1IVanuatu230 V50 HzFIG. 1IVenezuela120 V60 HzFIG. 1A, FIG. 1BVietnam127/220 V   50 HzFIG. 1A, FIG. 1C, FIG. 1GVirgin Islands115 V60 HzFIG. 1A, FIG. 1BWestern Samoa230 V50 HzFIG. 1IYemen, Rep. of220/230 V   50 HzFIG. 1A, FIG. 1D, FIG. 1GYugoslavia (Former)220 V50 HzFIG. 1C, FIG. 1FZambia230 V50 HzFIG. 1C, FIG. 1D, FIG. 1GZimbabwe220 V50 HzFIG. 1D, FIG. 1G
Various prior art commercial products have attempted to deal with the problem of fitting at least the most popular power plugs. Some use the Swiss-Army-Knife approach in which various kinds of plugs can be flipped out of a body for use. The Belkin Universal AC Travel Adapter is one such example. Others supply a variety kit of individual adapters, for example, the Targus APK01US Travel Connection Pack for Europe. The Kensington Travel Plug Adapter fits a revolver-type barrel on the end of a power cord and several sliders allow the user to extend the right plug out the distal end for over 150 different countries.
What is needed is a simple power plug that can be fitted on a cord that can simply and quickly plug into whatever plug arrangement is available.